its me again -.- help with another exponential question? :D

Solve the following equation:

http://latex.codecogs.com/gif.latex?...+3}=2^{1-x}+15

Answer: http://latex.codecogs.com/gif.latex?\dpi{150}%20x=1

I don't know what to do with the 15!!! (Headbang)

Help me? Pretty pleaseeee? (Wink)

Thank you very much!!

Re: its me again -.- help with another exponential question? :D

Hey pumbaa213.

Apart from trial and error, you will probably have to use a root finding algorithm. Have you come across this in class?

1 Attachment(s)

Re: its me again -.- help with another exponential question? :D

Re: its me again -.- help with another exponential question? :D

Quote:

Originally Posted by

**ibdutt**

Do you solve the last part with logarithms or have they not been taught when solving these? I just want to make sure I am not using anything that is ''not allowed''.

Re: its me again -.- help with another exponential question? :D

You don't need logarithms. It should be obvious that if $\displaystyle 2^x= 2$ then x= 1. (You do need to know that $\displaystyle y= a^x$, for a positive, is a "one-to-one function" to know that x= 1 is the **only** solution.

Re: its me again -.- help with another exponential question? :D

Quote:

Originally Posted by

**HallsofIvy** You don't need logarithms. It should be obvious that if $\displaystyle 2^x= 2$ then x= 1. (You do need to know that $\displaystyle y= a^x$, for a positive, is a "one-to-one function" to know that x= 1 is the **only** solution.

Okay, so we don't need logarithm until the answer becomes more complicated..Like x=2/3 or something. Right?

Re: its me again -.- help with another exponential question? :D

X is not equal to 1

2^4 is not equal to 0+15

If X = 0.9999 you get a close equality